| 17β-estradiol (E2) effects on in vitro thyroid hormone (TH) deiodination in various tissues were studied in 3 experiments (ExI, ExII, ExIII) for female and male rainbow trout at different states of sexual maturity. ExII trout were the biggest and most sexually mature (ripe ovaries), followed by ExI trout which were vitellogenic, and finally ExIII trout, which were previtellogenic and a different genetic stock from ExI and ExII. Trout were injected intraperitoneally on Days 1 and 3 with E2 in peanut oil or peanut oil alone, and sacrificed on Day 7. In ExI and ExII, one dose was used (0.5 mg E2/100 g body mass (bm)); in ExIII, 3 doses were used (0.05, 0.1 or 0.5 mg E2/100 g bm). Depending on the experiment, the activities of the following pathways were measured in vitro in liver, brain, gill, heart and kidney microsomes: T4-outer-ring deiodination (T4-ORD), producing 3,5,3′-triiodothyronine (T3, the biologically active TH) from thyroxine (T4, the secreted prohormone); T4-inner-ring deiodination (T4-IRD), producing inactive 3,3′,5′-triiodothyronine (rT3); T3-IRD, producing inactive 3,3′ -diiodothyronine (T2); rT3-ORD, producing inactive T2. (Abstract shortened by UMI.)... |
